The present invention relates to a method for producing lamella packets of the type normally used in adjustable steering columns in automobiles, which prevent slippage and unintended adjustment of the steering column by means of a plurality of friction surfaces. The lamella packets comprise a soft lamella made of a relatively soft sheet metal material and at least one hard lamella placed thereon and made of a relatively hard sheet metal material. The lamellae in the packets are joined by at least one rivet, which is formed, respectively, from the soft lamella.
Such lamella packets are known in the art and comprise on the one hand packets with so-called longitudinal lamellae and on the other hand packets with so-called height lamellae. The individual lamellae within the packets are spaced apart by a distance corresponding approximately to their thickness. One packet of longitudinal lamellae and one packet of height lamellae, respectively, form an associated pair. The two packets of each pair are then pushed together such that longitudinal lamellae and height lamellae alternate in the stack. On their mutual contact surfaces, the lamellae are in part provided with specially structured friction surfaces.
A pair each of the aforementioned lamella packets is arranged on either side of a so-called guide box, which holds the bearings for the steering column. Each longitudinal lamella packet is fixed to the guide box by means of fastening eyes, while each height lamella pair is mounted to a support strap, which in turn is fixed to the chassis, also by means of fastening eyes. A tension bolt penetrates the guide box as well as all the lamellae. For this purpose, guide slots are provided on the lamellae.
The adjustability of the steering column is due to the fact that the mutually meshing lamella packets can be displaced as well as pivoted relative to one another. The displacement or pivoting range is limited by the length of the aforementioned guide slots in the lamellae. To fix the steering column in a desired position, the tension bolt is tightened so as to press together the aforementioned friction surfaces on the lamellae.
It goes without saying thatxe2x80x94for a given tension force of the tension boltxe2x80x94the resulting total friction force or holding force can be correlated with the number of lamellae in the lamella packets and adjusted in a simple manner by selecting this number.
To keep the lamellae in the prior art lamella packets spaced at the desired distance, some of them are provided with a collar that is formed out of the lamellar plane in the area of the aforementioned fastening eyes. The initially mentioned rivet by which the individual lamellae of each packet are held together is also formed by such a collar, which is shaped on one of the two outermost lamellae of each packetxe2x80x94the so-called soft lamellaxe2x80x94at one of the fastening eyes, to the point where it is capable of penetrating the corresponding fastening eyes of the remaining lamellae. On the far side of the opposite outermost lamella, this collar is then shaped outwardly around the edge of the fastening eye of that lamella.
The invention, as described in the claims, defines a manufacturing concept (method) that permits efficient automatic production and assembly of the lamella packets of the described type.
According to claim 1, this method is characterized, in particular, by the use of two successive presses. At a rate defined by the first press
a soft lamella is completely formed and stamped from a strip of the softer sheet metal material in the first press,
a soft lamella thus produced is transported to the second press,
at least one hard lamella is completely formed and stamped from a strip of the harder sheet metal material and placed over a soft lamella in the second press, and the riveted connection is produced.